murblanc commented on a change in pull request #1684: URL: https://github.com/apache/lucene-solr/pull/1684#discussion_r466864602
########## File path: solr/core/src/java/org/apache/solr/cluster/placement/Cluster.java ########## @@ -0,0 +1,46 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.solr.cluster.placement; + +import java.io.IOException; +import java.util.Optional; +import java.util.Set; + +/** + * <p>A representation of the (initial) cluster state, providing information on which nodes are part of the cluster and a way + * to get to more detailed info. + * + * <p>This instance can also be used as a {@link PropertyValueSource} if {@link PropertyKey}'s need to be specified with + * a global cluster target. + */ +public interface Cluster extends PropertyValueSource { + /** + * @return current set of live nodes. Never <code>null</code>, never empty (Solr wouldn't call the plugin if empty + * since no useful could then be done). + */ + Set<Node> getLiveNodes(); + + /** + * <p>Returns info about the given collection if one exists. Because it is not expected for plugins to request info about + * a large number of collections, requests can only be made one by one. + * + * <p>This is also the reason we do not return a {@link java.util.Map} or {@link Set} of {@link SolrCollection}'s here: it would be + * wasteful to fetch all data and fill such a map when plugin code likely needs info about at most one or two collections. + */ + Optional<SolrCollection> getCollection(String collectionName) throws IOException; Review comment: I will add this. To your use case: if the plugin knows the names of the predefined system collections not to colocate new replicas with, it can request them one by one by name. Where an iteration would be useful is if the plugin doesn't want to place replicas on any `Node` with replicas from any collection named `system-*-metric` for example. It would then have to iterate... I'm always thinking eventually SolrCloud will be scaling to hundreds of thousands collections per cluster so anything that's linear in execution with that number is not acceptable in such a case for placement computation. But I do understand it can be useful in low scale uses. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
